Valve Timing question

[hayesbd]

I have a 2001 V70 XC that recently suffered a rather catastrophic engine failure. My compression test revealed 0/100/0/60/190 psi on cylinders 1,2,3,4,5, respectively. The trouble codes (no surprise) were p0300, p0301, and p0303 (along with another unrelated code that is probably due to the ETM).

Anyway, since this happened suddenly while cruising along and since the engine compression is as bad as it is, I figured the timing belt has jumped some teeth and bent some valves. However, upon looking at the belt and the timing marks, I found something strange. The PO (or dealer) must have put the belt on purposely one tooth off on the exhaust side. Here is a shot of the intake side:
http://i263.photobucket.com/albums/ii154/hayeslnut/volvopics007_zpsa4a8a413.jpg (http://s263.photobucket.com/user/hayeslnut/media/volvopics007_zpsa4a8a413.jpg.html)

It's hard to see, but there is a red mark in addition to the green mark I made on the sprocket. So far, so good. However, on the exhaust side (variable timing), the PO made a red mark one tooth off from a punched dimple (bracketed by my green marks):
http://i263.photobucket.com/albums/ii154/hayeslnut/volvopics009_zps7bbf31cb.jpg (http://s263.photobucket.com/user/hayeslnut/media/volvopics009_zps7bbf31cb.jpg.html)

As you can see, the PO's red mark lines up with the timing mark, not the punch mark. Has anyone seen the exhaust side purposely set one tooth off? I ask this since the car has a sticker showing the last belt change and I assumed that the dealer had done this.

Also, I am now wondering what caused at least two cylinders to completely crap out at the same time. I am wondering whether the turbo has disintegrated and sent parts into the engine? Comments welcome.

Thanks,
Brian

[Astro14]

Doubt it's the turbo. I further doubt that it was set deliberately one tooth off...more likely the amateur wrench turning of the previous owner got the timing wrong. It's not an easy job...and this guy made it worse by messing up the marks.

The compression is low in 4 of 5 cylinders. I suspect, that since your timing is off, that you've got burnt valves in those cylinders and the fix is a rebuilt head, not turbo....I also suspect that the previous owner knew that the car wasn't right, that's why it was being sold...but that's because I am suspicious by nature, I suppose....

[DYZ]

One tooth off will normally throws a code. Plenty of ppl have done that when they change timing belt. It shouldn't kill your engine right away, but I'm not sure about its long term effect (ppl normally correct it soon after noticing the issue). I recently took out my head and had it rebuilt after one of the exhaust valve was burnt. It's not too bad a job as long as you take your time. You can buy a rebuilt head for around $500. The only special tool needed is the cam locking tool.

DYZ

[hayesbd]

Thanks for the replies. There were no codes suggesting cam timing issues while we have owned this car. I can understand a gradual degradation of a valve going bad, but have a bit of trouble believing that two valves burnt through at exactly the same time. Prior to this incident, the car ran normally with a smooth idle. Also, with regard to the sprocket that was off a tooth, it's the exhaust cam, which has a position sensor and VVT so the computer controls its timing. I was wondering if it was intentionally set wrong to help the VVT keeps its timing where it wanted? Oh well, I will find out when I pull the head. I'll post pics.

[Xheart]

Doubt it's the turbo. I further doubt that it was set deliberately one tooth off...more likely the amateur wrench turning of the previous owner got the timing wrong. It's not an easy job...and this guy made it worse by messing up the marks.

The compression is low in 4 of 5 cylinders. I suspect, that since your timing is off, that you've got burnt valves in those cylinders and the fix is a rebuilt head, not turbo....I also suspect that the previous owner knew that the car wasn't right, that's why it was being sold...but that's because I am suspicious by nature, I suppose....

Out of curiosity Astro.
What is the likelihood of this "exhaust" camshaft gear not installed correctly, hence the multiple colored marks on the gear?

[howardc64]

Looking at your pictures, I don't know that I call it 1 tooth off. The timing marks on the cam on this car is notoriously hard to read properly. The distance between the cam mark and the top belt cover mark is about 1 inch and the head sits at a slightly tilted angle. This easily creates a 1/2 tooth inaccuracy depending on the viewpoint angles. With the fender/PS and coolant reservoir in the way, it is impossible to get a perfect side on view and is generally viewed at a top down tilted angle. Your exhaust cam pictures shows exactly this because we can't really see the original marks on the cover due to the angle of the picture. We can only see the added green mark. Whenever I've done the timing belt job, after setting the intake side to be "dead on", the exhaust side always seem a little off. Like 1/2 tooth or so and depends on the view angle once again.

On your belt, the intake cam marks seems slightly to the left of the cover mark. If you rotate this slightly clockwise, the exhaust side might be about 1/2 tooth off. You can try to line up exhaust side perfectly on and see how much offset is on the intake side to get a feel if you are 1 or 1/2 tooth off. If it is say 1/2 tooth off, the belt installation may be proper.

Another really good way to check is to count the number of teeth between the cam marks and compare. I forgot what the correct count is at the moment. You might post the count and see if another member chimes in with the same count on an 01 (I think 02 is same, not sure about the 2.5T updated engine on 03+). I have an 01, maybe I'll take a look :)

If you had no codes prior with the timing set this way until the recent catastrophic failure, I'd doubt that timing was off.

[hayesbd]

Here is a better picture showing the exhaust cam alignment (I have not rotated the engine at all); the white arrow points to the punch mark. The green mark on the cam cover was done on the bench and lines up well with the internal notch. I put a green mark on each side of the cog's punch mark. As you can see, the red mark from the PO lines up very well, but the punch mark is clearly one tooth off. The real mystery (to me) is why on earth is there a red mark one tooth away from the punch mark? Was the PO that careless? It's also a mystery why Volvo did not mark these in a clearer way. The faint punch mark on the exhaust cog is really hard to see!

http://i263.photobucket.com/albums/ii154/hayeslnut/exhaust_zps98dd6968.jpg (http://s263.photobucket.com/user/hayeslnut/media/exhaust_zps98dd6968.jpg.html)

I also can see that if the VVT sprocket is a tooth off, the computer control could actively compensate. As you can see, the slots in the cog show quite a bit of travel, at least enough to account for one tooth being off. It would, of course, limit the amount of exhaust cam advance when the computer called for it, but maybe that is called for only under hard driving (which we certainly don't do with this wagon). I plan on putting it back together with the punch mark aligned unless someone can give a good reason why the red mark is one tooth off.

I hope to get the head pulled off tomorrow some time. Will post my findings then.

Thanks,
Brian

[Xheart]

I see Howard's take on this. The green marking on the cover is arbitrary.
Where is the original factory cover with the "real" notch, like the one at intake?
I am suspecting you are up for a surprise.
Goodluck!

[howardc64]

Here is a better picture showing the exhaust cam alignment (I have not rotated the engine at all); the white arrow points to the punch mark. The green mark on the cam cover was done on the bench and lines up well with the internal notch. I put a green mark on each side of the cog's punch mark. As you can see, the red mark from the PO lines up very well, but the punch mark is clearly one tooth off. The real mystery (to me) is why on earth is there a red mark one tooth away from the punch mark? Was the PO that careless? It's also a mystery why Volvo did not mark these in a clearer way. The faint punch mark on the exhaust cog is really hard to see!

http://i263.photobucket.com/albums/ii154/hayeslnut/exhaust_zps98dd6968.jpg (http://s263.photobucket.com/user/hayeslnut/media/exhaust_zps98dd6968.jpg.html)

I also can see that if the VVT sprocket is a tooth off, the computer control could actively compensate. As you can see, the slots in the cog show quite a bit of travel, at least enough to account for one tooth being off. It would, of course, limit the amount of exhaust cam advance when the computer called for it, but maybe that is called for only under hard driving (which we certainly don't do with this wagon). I plan on putting it back together with the punch mark aligned unless someone can give a good reason why the red mark is one tooth off.

I hope to get the head pulled off tomorrow some time. Will post my findings then.

Thanks,
Brian

Indeed, looks like 1 tooth off from this picture. When you pull the belt off off and reassemble -1 tooth between the cam marks, you can definitively confirm the new alignment is better.

And yes, why was the red mark there? And why you didn't get codes with 1 tooth being off? I believe most members that got 1 tooth off got CE light pretty quick afterwards.

[DYZ]

A mark is just a mark. The TRUE alignment reference is at the other end of the cam shaft where it has a slot. The slot on both exhaust and intake shaft needs to be parallel to the seam line between the cam cover and head when the crank mark is aligned. The cam locking tool makes sure that happens. If your cam gear was taken off at one time and was not put back exactly as before, the punch mark would become useless. If that's the case, someone put that red mark there to override the punch mark and to represent the new reference position on the cam gear.

DYZ

[Tahoe_XC]

[QUOTE=howardc64;170146] With the fender/PS and coolant reservoir in the way, it is impossible to get a perfect side on view and is generally viewed at a top down tilted angle.


Another really good way to check is to count the number of teeth between the cam marks and compare.

Totally agree with Howard, trying to line up by eye sight is problematic. When doing my 06 I found myself pulling the cover on my 04 to confirm distinances. Howard suggests counting teeth, I preferred a straight edge for accuracy. Was 170mm on the 2.5 engine.

[hayesbd]

A mark is just a mark. The TRUE alignment reference is at the other end of the cam shaft where it has a slot. The slot on both exhaust and intake shaft needs to be parallel to the seam line between the cam cover and head when the crank mark is aligned. The cam locking tool makes sure that happens. If your cam gear was taken off at one time and was not put back exactly as before, the punch mark would become useless. If that's the case, someone put that red mark there to override the punch mark and to represent the new reference position on the cam gear.

DYZ

DYZ,

Thanks for this. I will definitely get the tool now. If the cam gear is off a tooth, though, and the PO's red mark is really it, wouldn't the VVT be limited in one direction and not provide enough travel? If it did burn valves, maybe this explains it?

Thanks,
Brian

[JRL]

NO and STOP
One tooth off WILL ALWAYS throw a code.
Sometimes it takes a while, a few hundred miles but it WILL throw it.
It also will not ruin an engine
Stop fixating on this and find out what the real issue is

[Xheart]

Stop fixating on this and find out what the real issue is

hands down.

[DYZ]

Don't rush to buy the cam locking tool unless you want to pull the head yourself. I also don't think your timing is off since that would normally throw a code. It's really hard to speculate what happened unless you pull the head. The machine shop that did the valve job for me said mine was due to leaking stem seal. If you want to keep the car you either have to do a engine swap or do a value job.

DYZ

[hayesbd]

...just a quick update. I have a few more connections to undo to get the head completely off. However, it's becoming apparent that as I get into it more, there are a lot of things that need to be replaced (PCV components, etc.) and I am tallying up a potentially large amount of money. I do all my own work, but still am figuring that to get this back on the road will total more than $1100 in parts so far. The air side of the turbo is also pretty oily, so that's another can of worms if I have to rebuild it. All this is on a car with a transmission that is working, but shifting poorly. We've got 260K miles on the clock so we are probably going to scrap this car. I will still post my findings, but probably won't fix it.

Thanks for the help, though.

Brian

[DYZ]

There is no shame to junk the car considering the mileage. But if you want to keep it running, the best option is to swap in an used low mileage engine. Then again, you are betting on the transmission to hold up. FYI, when I last checked, an used engine can be had for around $700.

DYZ

[Xheart]

...
I am tallying up a potentially large amount of money. I do all my own work, but still am figuring that to get this back on the road will total more than $1100 in parts so far.
...


There will be more $$$ with these many miles. I will let it go free.

[hayesbd]

I got the head separated a bit today enough to see with the borescope that there are two burned valves on cylinder 1 and 3. Unfortunately, this one is going to that big parking lot in the sky...

Brian

[Astro14]

I got the head separated a bit today enough to see with the borescope that there are two burned valves on cylinder 1 and 3. Unfortunately, this one is going to that big parking lot in the sky...

Brian

That sucks...it's what I was afraid you would find...but it sucks....